Ronan Martin Griffin Berg

University of Copenhagen · Department of Biomedical Sciences

Ventilation-perfusion scintigraphy is a functional imaging biomarker that has the potential of captivating the heterogeneity of chronic obstructive pulmonary disease (COPD). It specifically images the distribution of ventilation and perfusion within the lungs, which is a critical pathophysiological component of COPD. The extent of ventilation defec...

Background: Severe immunopathology may drive the deleterious manifestations observed in the advanced stages of coronavirus disease 2019 (COVID-19) but are poorly understood. Objective: To phenotype leukocyte subpopulations and the cytokine milieu in the lungs and blood of critically ill patients with COVID-19 acute respiratory distress syndrome...

New findings: What is the topic of this review? The use of proning for improving pulmonary gas exchange in critically ill patients. What advances does it highlight? Proning places the lung in its 'natural' posture, and thus optimises the ventilation-perfusion distribution, which enables lung protective ventilation and the alleviation of potentiall...

Background: Many people recovering from COVID-19 experience prolonged symptoms, particularly breathlessness. We urgently need to identify safe and effective COVID-19 rehabilitative strategies. The aim of the current study was to investigate the potential rehabilitative role of inspiratory muscle training (IMT). Methods: 281 adults (46.6±12.2 yea...

Background: To what extent sex-related differences in cardiorespiratory fitness (CRF) impact postoperative patient mortality and corresponding implications for surgical risk stratification remains to be established. Methods: To examine this, we recruited 640 patients (366 males vs. 274 females) who underwent cardiopulmonary exercise testing prio...

Objectives High-intensity interval training (HIIT) during pulmonary rehabilitation in patients with chronic obstructive pulmonary disease (COPD) may alleviate the symptom burden, but the fidelity and tolerability of HIIT using long or short intervals in patients with COPD are unknown. Methods Twelve patients with moderate-to-severe COPD were inclu...

Objective: To identify PaCO2 trajectories and assess their associations with mortality in critically ill patients with coronavirus disease 2019 (COVID-19) during the first and second waves of the pandemic in Denmark. Design: A population-based cohort study with retrospective data collection. Patients: All COVID-19 patients treated in eight int...

New findings: What is the central question in this study? How reliable is the combined measurement of the pulmonary diffusing capacity to carbon monoxide and nitric oxide (DLCO/NO ) during exercise and in the resting supine position, respectively? What is the main finding and its importance? The DLCO/NO technique is reliable with a very low day-to...

In chronic obstructive pulmonary disease (COPD), the progressive loss of lung tissue is widely considered non-reversible. Thus, various treatment and rehabilitation schemes, including exercise-based pulmonary rehabilitation (PR) are thought to slow down but not reverse or halt the disease. Nonetheless, the adult lung conceals the intrinsic capacity...

Post COVID-19 condition can occur following infection with SARS-CoV-2 and is characterised by persistent symptoms, including fatigue, breathlessness and cognitive dysfunction, impacting everyday functioning. This study explored how people living with post COVID-19 experienced an eight-week inspiratory muscle training (IMT) rehabilitation programme....

A large proportion of patients exhibit persistently reduced pulmonary diffusion capacity after COVID-19. It is unknown whether this is due to a post-COVID restrictive lung disease and/or pulmonary vascular disease. The aim of the current study was to investigate the association between initial COVID-19 severity and haemoglobin-corrected diffusion c...

Dynamic cerebral autoregulation is often assessed by continuously recorded arterial blood pressure (ABP) and transcranial Doppler-derived mean cerebral blood flow velocity followed by analysis in the time and frequency domain, respectively. Sequential correlation (in the time domain, yielding e.g., the measure mean flow index, Mxa) and transfer fun...

Aim: Skeletal muscle convective and diffusive oxygen (O 2 ) transport are peripheral determinants of exercise capacity in both patients with chronic obstructive pulmonary disease (COPD) and chronic heart failure (CHF). We hypothesised that differences in these peripheral determinants of performance between COPD and CHF patients are revealed during...

Objective Invasively measured arterial blood pressure (ABP) is associated with complications, while non-invasively measured ABP is generally considered risk-free. This study aimed to investigate the reliability of non-invasive ABP measured using finger-cuff volume-clamp device compared to invasive ABP measured by an arterial catheter in patients wi...

Mechanisms of COVID-19-induced lung injury involve complex immunopathological events which are currently being elucidated. Studying immune mechanisms at the primary site of injury, i.e. the lower airways, are particularly informative. This review provides a brief introduction to the methods used to perform sampling from the lungs of critically ill...

The effects of dexamethasone (DXM) treatment on pulmonary immunity in COVID-19–associated acute respiratory distress syndrome (CARDS) remain insufficiently understood. We performed transcriptomic RNA-seq analysis of bronchoalveolar lavage fluid from 20 mechanically ventilated patients: 12 with CARDS (with or without DXM) and 8 non–COVID-19 critical...

New findings: What is the topic of this review? To explore the relationships and physiological mechanisms underlying the clinical benefits of cardiorespiratory fitness (CRF) in patients undergoing major intra-abdominal surgery. What advances does it highlight? Elevated CRF reduces postoperative morbidity/mortality, thus highlighting the importance...

To provide novel data on surfactant levels in adult COVID-19 patients, we collected bronchoalveolar lavage fluid less than 72 h after intubation and used Fourier Transform Infrared Spectroscopy to measure levels of dipalmitoylphosphatidylcholine (DPPC). A total of eleven COVID-19 patients with moderate-to-severe ARDS (CARDS) and 15 healthy controls...

Introduction In the early phase after severe brain injury, patients are often bedridden in an attempt to control intracranial homeostasis; however, prolonged immobilisation may trigger complications. There is limited knowledge about the physiological effects of mobilisation in this early phase. Objective To investigate changes in brain tissue oxyg...

Dynamic cerebral autoregulation to spontaneous fluctuations in cerebral perfusion pressure (CPP) is often assessed by transcranial Doppler (TCD) in the time domain, yielding primarily the mean flow index (Mx), or in the frequency domain using transfer function analysis (TFA), yielding gain and phase. For both domains, the measurement of blood press...

Background: It is unknown whether the complex immunopathogenesis of COVID-19 acute respiratory distress syndrome (CARDS) differs from that of non-COVID-19 ARDS. Moreover, the effects of systemic dexamethasone (DXM) treatment on pulmonary immunity in COVID-19 remain insufficiently understood. Objective: To understand immune regulation in the lungs o...

Introduction COVID-19 is associated with a marked systemic inflammatory response with concomitant cardiac injury and remodelling, but it is currently unknown whether the latter is reversible. Given that high-intensity interval training (HIIT) is a powerful stimulus to improve cardiorespiratory fitness while also eliciting marked anti-inflammatory e...

Understanding of strategies to support individuals recovering from coronavirus disease 2019 (COVID-19) is limited. ‘Long COVID’ is a multisystem disease characterised by a range of respiratory, gastrointestinal, cardiovascular, neurological, and musculoskeletal symptoms extending beyond 12 weeks. The aim of this study was to explore individuals’ ex...

Cerebral autoregulation is a complex mechanism that serves to keep cerebral blood flow relatively constant within a wide range of cerebral perfusion pressures. The mean flow index (Mx) is one of several methods to assess dynamic cerebral autoregulation, but its reliability and validity have never been assessed systematically. The purpose of the pre...

In patients with severe traumatic brain injury, there is limited evidence of the clinical effect of early orthostatic exercise, although such exercise may strengthen systemic or cerebral hemodynamic responses to head-up tilt, thereby minimizing orthostatic intolerance. We measured dynamic cerebral autoregulation (dCA) and the occurrence of orthosta...

Collaborative teaching strategies such as peer instruction and conventional group work have previously been shown to enhance meaningful learning, but they have not previously been compared. In this present study, we compared the impact of solving quizzes with peer instruction and conventional group work on immediate learning in a laboratory exercis...

Objectives: Many patients with COVID-19 suffer from persistent symptoms, many of which may potentially be reversed by high-intensity interval training (HIIT). Yet, the safety and tolerability of HIIT after COVID-19 is controversial. This study aimed to investigate the fidelity, tolerability and safety of three different HIIT protocols in individua...

It is a common but flawed presumption that blood lactate reflects the lactic acid production in the body's tissues. Lactate is formed directly from pyruvate and functions to dampen reductions in intracellular pH through lactate-H+ cotransport to the extracellular space. Though this may give rise to elevated blood lactate, increased lactate producti...

New findings: What is the central question of this study? How does recurrent contact incurred across a season of professional rugby union impact molecular, cerebrovascular and cognitive function? What is the main findings and its importance? A single season of professional rugby union increases systemic oxidative-nitrosative stress (OXNOS) confirm...

Hyperlactataemia It is a common but flawed presumption that blood lactate reflects the lactic acid production in the bodyʼs tissues. Lactate is formed directly from pyruvate and functions to dampen reductions in intracellular pH through lactate- H+ cotransport to the extracellular space. Though this may give rise to elevated blood lactate, increas...

Background: Mean flow index (Mxa) for evaluating dynamic cerebral autoregulation is derived using varying approaches for calculation, which may explain that the reliability ranges from poor to excellent. The comparability, repeatability, stability, and internal consistency of approaches have not previously been assessed. Methods: We included 60...

New findings: What is the topic of this review? Lactate is considered an important substrate for mitochondria in muscles, heart, and brain during exercise, and is the main gluconeogenetic precursor in the liver and kidneys. In this light, we review the (patho)physiology of lactate metabolism in sepsis and coronavirus disease 2019 (COVID-19). What...

The transcranial Doppler ultrasound-derived mean flow index (Mxa) is widely used for assessing dynamic cerebral autoregulation (dCA) in different clinical populations. This study aimed at estimating the relative and absolute reliability of Mxa in healthy participants in the supine position and during head-up tilt (HUT). Fourteen healthy participant...

99mTc-dimercaptosuccinic acid (DMSA) scintigraphy is currently the method of choice for assessing renal scarring in children, but it is not established whether conducting the scan as a single photon emission tomography combined with low-dose CT (SPECT/ldCT) scan provides additional diagnostic benefits when compared to conventional planar scintigrap...

Background Ventilation‐perfusion (VQ) scintigraphy and lung function testing are often used to assess allograft function after single lung transplantation (SLTX). However, it is unknown whether allograft defects on VQ scintigraphy presage all‐cause mortality after SLTX. Objective To investigate whether allograft defects on VQ scintigraphy portend...

Asymptomatic aortic stenosis (AS) is a frequent condition that may cause hyponatremia due to neurohumoral activation. We examined if hyponatremia heralds poor prognosis in patients with asymptomatic AS, and whether AS in itself is associated with increased risk of hyponatremia. The study question was investigated in 1,677 individuals that had and a...

Stetoskopet om halsen er indbegrebet af en læge, og vi bruger det flittigt. Samtidig ved vi, at kvaliteten af vores fund kan vaere tvivlsom. Men stetoskopi er stadig et vigtigt diagnostisk redskab, hvis det bruges korrekt og systematisk.

Introduction Preoperative cardiopulmonary exercise testing aids surgical risk stratification and is an established predictor of mid- to long-term survival in patients undergoing elective open abdominal aortic aneurysm repair. Whether cardiopulmonary exercise testing also predicts 30-day mortality in this population remains to be established. Mater...

New findings: What is the central question of this study? Can the change in haemoglobin's affinity for oxygen in the human cerebral circulation be modelled in vivo? What is the main finding and its importance? We provide a novel method for modelling the oxyhaemoglobin dissociation curve at the cerebral capillary level in humans, so that the cerebr...

In the present study, we compared estimates of split renal function (SRF) in paediatric patients of various diagnostic subgroups by 99mTc-dimercaptosuccinic acid (DMSA) scintigraphy using either geometric mean (GM) based on planar scans or a volume of interest (VOI)-based analysis on single photon emission tomography combined with low-dose CT (SPEC...

Hypoxaemia is present in many critically ill patients, and may contribute to encephalopathy. Changes in the passage of large neutral amino acids (LNAAs) across the blood-brain barrier (BBB) with an increased cerebral influx of aromatic amino acids into the brain may concurrently be present and also contribute to encephalopathy, but it has not been...

According to the ‘middle ground hypothesis’ formulated by the neuroscientist E. Paul Zehr, case studies from popular culture may facilitate discovery learning in physiology education. In the present chapter, I present and evaluate the use of Darth Vader from the Star Wars saga and Miles Dyson from the Terminator franchise for teaching respiratory a...

Objective: To compare the effect of a conventional to an intensive blood pressure monitoring regimen on blood pressure in hypertensive patients in the general practice setting. Design: Randomized controlled parallel group trial with 12-month follow-up. Setting: One hundred and ten general practices in all regions of Denmark. Participants: On...

The systemic inflammatory response triggered by lipopolysaccharide (LPS) is associated with cerebral vasoconstriction, but the underlying mechanisms are unknown. We therefore examined whether a four-hour intravenous LPS infusion (0.3 ng kg^-1) induces any changes in the transcerebral net exchange of the vasoactive peptides endothelin-1 (E...

We reassessed data from a previous study on the transcerebral net exchange of large neutral amino acids (LNAAs) using a novel mathematical model of blood–brain barrier (BBB) transport. The study included twelve healthy volunteers who received a 4-h intravenous lipopolysaccharide (LPS) infusion (total dose: 0·3 ng/kg), a human experimental model of...

Post-transplantation mortality after lung transplantation (LTX) is higher than for other solid organ transplantations. Thoracic surgery is associated with increased risk of thromboembolic complications, and since LTX recipients lack the collateral bronchial circulation, pulmonary thromboembolism (PTE) may represent a pertinent yet largely under-dia...

CD163 is the macrophage receptor for uptake of hemoglobin-haptoglobin complexes. The human receptor can be shed from the macrophage surface owing to a cleavage site for the inflammation-inducible TACE/ADAM17 enzyme. Accordingly, plasma ‘soluble CD163’ (sCD163) has become a biomarker for macrophage activity and inflammation. The present study disclo...

The exact mechanism linking the systemic inflammatory response associated with sepsis to changes in lung function remains to be determined. In a human experimental model of inflammation, we investigated how acute systemic and local pulmonary inflammation affects ventilatory capacity and pulmonary gas exchange. Fifteen volunteers received Escherichi...

case studies from popular culture have proven to be useful tools for conveying various physiological concepts to undergraduate physiology and medical students ([16][1]). This motivated us to use Anakin Skywalker, also known as Darth Vader, from the Star Wars saga to teach respiratory physiology ([1

The present paper presents a mechanistic model of cerebral autoregulation, in which the dual effects of the arachidonic acid metabolites 20-hydroxyeicosatetraenoic acid (20-HETE) and epoxyeicosatrienoic acids (EETs) on vascular smooth muscle mediate the cerebrovascular adjustments to a change in cerebral perfusion pressure (CPP). 20-HETE signalling...

In sepsis, higher PaCO2 levels are associated with impaired dynamic cerebral autoregulation (dCA), which may expose the brain to hypo- and hyperperfusion during acute fluctuations in blood pressure. We hypothesised that short-term mechanical hyperventilation would dCA in critically ill patients with sepsis. Seven mechanically ventilated septic pati...

Objective: In the present hypothesis-generating study, we investigated whether spontaneous blood pressure oscillations are suppressed to lower frequencies, and whether abolished oscillations are associated with an adverse outcome in mechanically ventilated patients with sepsis. Methods: We retrospectively subjected invasive steady-state blood pr...

Background Cerebral hemodynamic disturbances in the peri- or postoperative period may contribute to postoperative cognitive dysfunction (POCD) in patients undergoing coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB). We therefore examined dynamic cerebral autoregulation (dCA) post-CPB and changes in neurocognitive function in...

Observational clinical studies suggest the initial phase of sepsis may involve impaired cellular immunity. In the present study, we investigated temporal changes in T-cell subsets and T-cell cytokine production during human endotoxemia. Endotoxin (Escherichia coli lipopolysaccharide 4 ng/kg) was administered intravenously in 15 healthy volunteers....